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2018 Sierra 1500 Transmission Fluid Change - Rough Shifting at 85k Miles

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Mike T. · rep 0 · May 22, 3:45 AM · 1 replies · solved · Question

Vehicle: 2018 GMC Sierra 1500 SLT

Hey everyone, I've got a 2018 GMC Sierra 1500 SLT with the 5.3L V8 and about 85,000 miles on it. Lately, I've noticed some slightly rougher shifts, especially between 2nd and 3rd gear, and sometimes a bit of hesitation when accelerating from a stop.

I'm wondering if it's time for a transmission fluid and filter change. The owner's manual suggests checking it, but doesn't give a super clear interval for replacement under normal conditions. I do a fair bit of towing with a small utility trailer occasionally, which I know can put extra stress on the transmission.

Has anyone else experienced similar symptoms with their Sierra around this mileage? Is this something I can tackle myself, or is it better left to a professional? Any specific fluid recommendations or things to watch out for during the process?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 3:45 AM

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ClearTheCode admin answer:

Rough shifting and hesitation at 85,000 miles, especially with occasional towing, are common indicators that your transmission fluid might be degrading. A fluid and filter change is a good preventative measure and can often resolve these symptoms.

Causes of Rough Shifting:

  • Degraded Transmission Fluid: Over time, fluid loses its lubricating properties and can accumulate contaminants, leading to increased friction and poor shifting.
  • Clogged Transmission Filter: A dirty filter restricts fluid flow, causing pressure issues within the transmission.
  • Low Fluid Level: Insufficient fluid can lead to overheating and improper operation.

DIY Steps for Transmission Fluid & Filter Change (General Guide):

  1. Gather Supplies: You'll need new transmission fluid (typically Dexron VI for your Sierra), a new transmission filter, a new pan gasket, a drain pan, wrenches, and possibly a torque wrench.
  2. Warm Up the Vehicle: Drive for a few minutes to get the fluid to operating temperature, which helps it drain more completely.
  3. Drain Fluid: Place a large drain pan under the transmission. Remove the drain plug (if present) or carefully loosen the pan bolts to allow fluid to drain.
  4. Remove Pan & Filter: Once most fluid is drained, remove all pan bolts. Be prepared for more fluid to spill. Carefully lower the pan. Remove the old filter.
  5. Clean Pan & Magnet: Clean the transmission pan thoroughly, removing any old gasket material. Clean the magnet inside the pan, which collects metallic wear particles.
  6. Install New Filter & Gasket: Install the new transmission filter. Place the new gasket on the pan and reinstall the pan, tightening bolts to factory specifications.
  7. Refill Fluid: Using a funnel, add the recommended amount of new transmission fluid through the dipstick tube. Start the engine, cycle through gears, and recheck the fluid level, adding more as needed until it's at the correct mark on the dipstick.

When to See a Shop:

  • If symptoms persist or worsen after the fluid and filter change.
  • If your check engine light illuminates with transmission-related diagnostic trouble codes (DTCs) such as P0700 (Transmission Control System Malfunction), P0741 (Torque Converter Clutch Circuit Performance), or P0776 (Pressure Control Solenoid 'B' Performance).
  • If you prefer a full transmission flush, which requires specialized equipment not typically available to DIYers. While a pan drop and filter change replaces a significant portion of the fluid, a flush replaces nearly all of it.
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